SiC Seed Substrate Hot Self-Split for Reuse Without Wafer Cracks
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Solution Overview
Problem
The high cost of SiC growth substrates hinders the market expansion of SiC power semiconductors, necessitating a cost-effective method for their use in manufacturing.
Innovation Solution
A hot self-split process is employed to separate a thin SiC seed region from a thick SiC growth substrate using a stealth laser and wafer bonding, allowing reuse of the SiC growth substrate, thereby reducing manufacturing costs and improving quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SiC growth substrates are used for manufacturing SiC power semiconductors, then high quality and high performance are achieved, but manufacturing cost increases significantly
Solution Approach 1:
The SiC substrate is divided into two functional regions: a thick growth substrate region for cost-effective mass production and a thin seed region for device fabrication. This segmentation allows the expensive seed substrate to be reused by separating and reattaching it to new growth substrates, thereby reducing overall manufacturing costs while maintaining high device quality
Solution Approach 2:
Instead of discarding the expensive SiC seed substrate after single use, the patent recovers it by separating the thin seed region from the thick growth substrate. The recovered seed substrate can then be reused for subsequent device fabrication processes, significantly reducing manufacturing costs while preserving the high-quality characteristics that enable high performance
2Ease of repair
If a thin SiC seed region is separated from a thick SiC growth substrate using conventional methods, then substrate reuse is possible, but external force causes wafer cracks and defects
Solution Approach 1:
The patent utilizes phase transition of water from liquid to vapor through rapid heating by a flash lamp. This phase transition generates explosive vapor pressure that mechanically separates the thin seed region from the thick growth substrate along the interface, achieving crack-free separation without applying external mechanical force to the wafer
Solution Approach 2:
Conventional mechanical separation methods that apply external force directly to the wafer are replaced with a thermal-field-based method. A flash lamp rapidly heats the wafer, causing water between the layers to vaporize and generate internal pressure that drives the separation, thereby eliminating the need for external mechanical force and preventing wafer cracks
3Reliability
If conventional separation methods are used without external force, then wafer cracks are avoided, but separation of thin seed region from thick growth substrate is difficult to achieve
Solution Approach 1:
The patent exploits the phase transition of water from liquid to vapor through rapid thermal heating. The explosive vapor pressure generated during this phase transition provides the necessary mechanical force to efficiently separate the thin seed region from the thick growth substrate along their interface, achieving both high wafer integrity and high separation efficiency
Solution Approach 2:
The flash lamp heating is applied as a periodic, pulsed action rather than continuous heating. This periodic thermal input allows controlled vaporization of water at the interface, generating repeated pressure pulses that effectively drive the separation process while maintaining wafer integrity through precise timing and energy control
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process enables the reuse of SiC growth substrates, enhancing quality uniformity and preventing defects like wafer cracks, leading to a significant reduction in manufacturing costs while maintaining high performance.
Implementation Method 1
a seed substrate reforming step of irradiating a stealth laser into the inside of the SiC seed substrate to form a reforming layer parallel to a growth plane of the SiC seed substrate
Implementation Method 2
an upper temporary substrate bonding step of bonding an upper temporary substrate to an upper surface of the device region via an upper bonding layer
Implementation Method 3
the seed region separation step is performed without an external force by thermal/mechanical stress due to a difference in thermal expansion rate and thickness on both sides of the reforming layer as a boundary
Data Source
AI summary
Embodiments according to the present invention comprise a step of preparing a SiC seed substrate having conductivity; a device region forming step; a first fab process step including a doping process for a SiC power semiconductor device and an electrode forming process in the device region; a seed substrate reforming step; an upper temporary substrate bonding step; and a seed region separation step of separating the SiC seed substrate with the reforming layer as a boundary to form a seed region; and wherein the seed region separation step is performed in a process of cooling from a bonding temperature for bonding the upper temporary substrate, and separation is performed without an external force by thermal/mechanical stress due to a difference in thermal expansion rate and thickness on both sides of the reforming layer as a boundary.